132 AGRICULTURAL RESEARCH AND THE FARMER : 



a ready sale because there is a demand for a low-priced cheese, 

 and in the absence of knowledge the demand is satisfied by a 

 cheese of low quahty. But it ought to be just as cheap to produce 

 a good cheese as a bad one ; the main difficulty is that so little 

 is known of the chemistry of cheese-making, and consequently 

 the methods of manufacture now followed are, from the scientific 

 standpoint, rather crude. In making cheese, the important factor 

 on which almost all stages in the process depend is " acidity."* 

 The first stage in the process, for example, usually consists in 

 adding a " starter " to the milk, the " starter " containing bacteria 

 which control the acidity of the milk. The next stage is the 

 addition of an enzyme, rennet, which coagulates the milk. 

 Subsequent operations, which vary with the type of cheese being 

 produced, are done at various stages in the development of 

 acidity. Finally, the flavour and texture of the cheese depend 

 largely on the degree of acidity. Now at present we have no 

 definite information as to the ranges of acidity which are proper 

 to the various stages in the process of cheese-making. In commer- 

 cial practice, acidity can only be determined in the earlier stages, 

 during which whey can be separated from the product, and even 

 then the means employed are crude and uncertain. One popular 

 method, for example, is to draw out " threads " from the curd 

 with a hot iron, and the degree of acidity is guessed from the length 

 of the threads. Even in the most modern cheese factories, the best 

 method employed at present is one of " titration." This method 

 is technically unsound because it only measures the amount of the 

 acidity, which bears no necessary relation to the intensity of the 

 acidity, and it is the latter which is the vital factor. The cheese 

 manufacturer is not to blame, for until more is known regarding 

 the ranges of acidity desired at the various stages, and the methods 

 by which they can be determined, there is no other course for him 

 to follow, and he must remain dependent on chance — as he 

 practically is at present — for the production of cheese of the 

 required quality and flavour, and particularly for the occurrence 

 of the welcomed fungus which gives the blue-veins in Stiltons. 



The subject is a wide one and involves much difficult investi- 

 gation before results are obtainable which can be used in practice. 

 The methods employed are too technical to be described in 

 detail in a pubHcation of this character, but it may be said that 

 the Reading workers have approached the question by investigat- 

 ing the ranges of acidity required for the growth of the organisms 

 responsible for the undesirable discoloration of Stilton cheese. 



* We use the term " acidity " because it is the one usually employed, 

 although scientifically it is a loose term and may lead to errors in 

 description. 



